It's easy to get caught up in all the gory mess of zombies when thinking about "The Walking Dead," but it's the characters that drive the story in Robert Kirkman's post-apocalyptic tale. With production on the first season well underway, fans have already been introduced to several of the main actors starring in the developing AMC adaptation — like Andrew Lincoln as Rick Grimes, for example — but there are a few characters still waiting to surprise you.

Take Amy and Andrea, for instance, a pair of sisters played by Emma Bell and Laurie Holden respectively on the Frank Darabont-directed series. MTV News spoke with Bell and Holden about their characters and what drives the two of them to forge such a close bond.

"[Andrea is] the older sister, so she's the protective one," Bell told MTV. "She's protective of me. I'm the kind of emotionally crumbling — not crumbling, but my character is a little bit younger and has these emotional moments, and [Andrea] is always kind of there to be my rock. Our characters really rely on each other."

"She's my heart," added Holden. "We don't know if our parents have survived the apocalypse and she was going to college, and [my character] decided it would be a great idea to bond and go on this road trip, and all hell broke loose on the trip. We got stranded on the side of the road."

"For me, it's been very hard, because I love her madly and I feel so responsible — if anything happens to her, it's my fault, because we could have flown, and it was my 'great idea' to drive," she continued. "I'm a big sister, but I also become like a mama bear. I've gotta make sure that she's okay, and I'm crumbling inside, but I can't let her see it. I've got to be strong for her."

Tell us which characters you're most excited to see on "The Walking Dead" in the comments section and on Twitter!